Probiotics are widely consumed and the widespread advertising is often not really justified by the evidence. Many products
were never studied as such and some companies use studies performed with other (and different) products for advertising even
during medical conventions. Evidence of benefit is still patchy and the clinician has to take into account the variability
of the strains, the doses, the quality of the trials and clinical relevance of end points.

In this issue of Gut, Mohayyedi and colleagues (see page 325) have made an interesting systematic analysis on the randomised controlled trials testing various probiotics in patients with
irritable bowel syndrome (IBS).1 They show that many trials are of good quality, that positive results were obtained with some strains, or products combining
several strains, but also that studies are heterogeneous and that funnel plot asymmetry suggests biases in the publications
(ie, there are more reports on the positive studies than of the negative ones). I agree with the authors that meta-analysis
is not wise as the active ingredients and mechanisms of action of various probiotics are very likely to …